perf(runtime): pool the local xray gRPC connection (#6916)

A client per runtime operation made a bulk delete pay a TCP and HTTP/2
handshake for every client. The local runtime now keeps one gRPC client
per API port and replaces it when a core restart moves the port; the
traffic poll keeps its own client, since StatsLastValues is unlocked.

A pooled channel keeps grpc-go's reconnect backoff after the core
restarts, so a call that fails with Unavailable drops the client and
dials again, as a client per call did.

internal/web/runtime/local.go

@@ -8,6 +8,9 @@ import (
 	"strings"
 	"sync"
 
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
 	"github.com/mhsanaei/3x-ui/v3/internal/amneziawg"
 	"github.com/mhsanaei/3x-ui/v3/internal/amneziawgnet"
 	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
@@ -41,12 +44,22 @@ func (l *Local) withAPI(fn func(api *xray.XrayAPI) error) error {
 	if port <= 0 {
 		return errors.New("local xray is not running")
 	}
-	var api xray.XrayAPI
-	if err := api.Init(port); err != nil {
+	api, err := localAPIForPort(port)
+	if err != nil {
 		return err
 	}
-	defer api.Close()
-	return fn(&api)
+	err = fn(api)
+	if status.Code(err) != codes.Unavailable {
+		return err
+	}
+	// A pooled channel keeps grpc-go's reconnect backoff after a core restart and fails fast for
+	// seconds; drop it and dial again, as a client per call did.
+	evictLocalAPIClient(api)
+	api, err = localAPIForPort(port)
+	if err != nil {
+		return err
+	}
+	return fn(api)
 }
 
 func (l *Local) AddInbound(_ context.Context, ib *model.Inbound) error {

internal/web/runtime/local_api.go

@@ -0,0 +1,52 @@
+package runtime
+
+import (
+	"sync"
+
+	"github.com/mhsanaei/3x-ui/v3/internal/xray"
+)
+
+// One pooled gRPC client serves local runtime operations; never use it for traffic stats, whose
+// unlocked StatsLastValues a second reader would corrupt, so the traffic poll keeps its own client.
+var (
+	localAPIMu     sync.Mutex
+	localAPIPort   int
+	localAPIClient *xray.XrayAPI
+)
+
+// localAPIForPort returns the pooled client for the API port, replacing (and closing) it when a core
+// restart moved the port; callers must not close it.
+func localAPIForPort(port int) (*xray.XrayAPI, error) {
+	localAPIMu.Lock()
+	defer localAPIMu.Unlock()
+
+	if localAPIClient != nil {
+		if localAPIPort == port {
+			return localAPIClient, nil
+		}
+		localAPIClient.Close()
+		localAPIClient = nil
+	}
+
+	api := &xray.XrayAPI{}
+	if err := api.Init(port); err != nil {
+		return nil, err
+	}
+	localAPIClient = api
+	localAPIPort = port
+	return api, nil
+}
+
+// evictLocalAPIClient closes the pooled client so the next call dials a fresh connection, unless
+// another call already replaced the one that failed.
+func evictLocalAPIClient(api *xray.XrayAPI) {
+	localAPIMu.Lock()
+	defer localAPIMu.Unlock()
+
+	if localAPIClient != api {
+		return
+	}
+	localAPIClient.Close()
+	localAPIClient = nil
+	localAPIPort = 0
+}

internal/web/runtime/local_api_test.go

@@ -0,0 +1,117 @@
+package runtime
+
+import (
+	"context"
+	"net"
+	"strconv"
+	"testing"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
+	"github.com/xtls/xray-core/app/proxyman/command"
+
+	"github.com/mhsanaei/3x-ui/v3/internal/xray"
+)
+
+// A client per operation made a bulk delete pay a TCP + HTTP/2 handshake per client, so the local
+// runtime's client must stay open and be reused between calls.
+func TestLocalWithAPIKeepsTheClientOpen(t *testing.T) {
+	port := 63211
+	local := NewLocal(LocalDeps{APIPort: func() int { return port }})
+
+	var api *xray.XrayAPI
+	if err := local.withAPI(func(a *xray.XrayAPI) error { api = a; return nil }); err != nil {
+		t.Fatalf("withAPI: %v", err)
+	}
+	if api.HandlerServiceClient == nil {
+		t.Fatal("the client was closed when the call returned; a pooled client must stay open")
+	}
+}
+
+func TestLocalWithAPIReusesOneClient(t *testing.T) {
+	port := 63212
+	local := NewLocal(LocalDeps{APIPort: func() int { return port }})
+
+	clients := make([]*xray.XrayAPI, 0, 3)
+	for range 3 {
+		if err := local.withAPI(func(a *xray.XrayAPI) error {
+			clients = append(clients, a)
+			return nil
+		}); err != nil {
+			t.Fatalf("withAPI: %v", err)
+		}
+	}
+	for i, c := range clients {
+		if c != clients[0] {
+			t.Fatalf("call %d got a different client; the local gRPC connection must be pooled", i)
+		}
+	}
+}
+
+// A core restart can move the API port, so the pool has to follow it and close
+// the client it replaces instead of leaking it.
+func TestLocalWithAPIEvictsTheClientWhenThePortChanges(t *testing.T) {
+	port := 63213
+	local := NewLocal(LocalDeps{APIPort: func() int { return port }})
+
+	var first *xray.XrayAPI
+	if err := local.withAPI(func(a *xray.XrayAPI) error { first = a; return nil }); err != nil {
+		t.Fatalf("withAPI: %v", err)
+	}
+	port = 63214
+	var second *xray.XrayAPI
+	if err := local.withAPI(func(a *xray.XrayAPI) error { second = a; return nil }); err != nil {
+		t.Fatalf("withAPI after the port change: %v", err)
+	}
+	if first == second {
+		t.Fatal("a changed API port must not reuse the old client")
+	}
+	if first.HandlerServiceClient != nil {
+		t.Fatal("the evicted client must be closed, not leaked")
+	}
+}
+
+type fakeHandlerServer struct {
+	command.UnimplementedHandlerServiceServer
+}
+
+func (fakeHandlerServer) RemoveInbound(context.Context, *command.RemoveInboundRequest) (*command.RemoveInboundResponse, error) {
+	return &command.RemoveInboundResponse{}, nil
+}
+
+// startFakeCore serves the core's handler service on port (0 picks a free one).
+func startFakeCore(t *testing.T, port int) (int, func()) {
+	t.Helper()
+	listener, err := net.Listen("tcp", net.JoinHostPort("127.0.0.1", strconv.Itoa(port)))
+	if err != nil {
+		t.Fatalf("listen on %d: %v", port, err)
+	}
+	server := grpc.NewServer()
+	command.RegisterHandlerServiceServer(server, fakeHandlerServer{})
+	go func() { _ = server.Serve(listener) }()
+	return listener.Addr().(*net.TCPAddr).Port, server.Stop
+}
+
+// A pooled channel kept grpc-go's reconnect backoff after a core restart and failed fast for
+// seconds; the first call after the restart must succeed, as it did with a client per call.
+func TestLocalWithAPIRecoversAfterTheCoreRestarts(t *testing.T) {
+	port, stop := startFakeCore(t, 0)
+	local := NewLocal(LocalDeps{APIPort: func() int { return port }})
+	delInbound := func(api *xray.XrayAPI) error { return api.DelInbound("tag") }
+
+	if err := local.withAPI(delInbound); err != nil {
+		t.Fatalf("first call: %v", err)
+	}
+	stop()
+	if err := local.withAPI(delInbound); status.Code(err) != codes.Unavailable {
+		t.Fatalf("a call while the core is down: got %v, want Unavailable", err)
+	}
+
+	_, stopRestarted := startFakeCore(t, port)
+	t.Cleanup(stopRestarted)
+	if err := local.withAPI(delInbound); err != nil {
+		t.Fatalf("the first call after the core restarted must succeed: %v", err)
+	}
+}